Microscopic-observation drug-susceptibility assay for the diagnosis of drug-resistant tuberculosis in Harare, Zimbabwe

• Published in: PloS one 2013-02, Vol.8 (2), p.e55872-e55872
• Main Authors: Makamure, Beauty, Mhaka, Jesca, Makumbirofa, Salome, Mutetwa, Reggie, Mupfumi, Lucy, Mason, Peter, Metcalfe, John Z
• Format: Article
• Language: English
• Subjects: Accuracy; Adult; Antitubercular agents; Antitubercular Agents - pharmacology; Assaying; Biomedical research; Coinfection; Culture; Diagnosis; Diagnostic systems; Drug resistance; Drug Resistance, Bacterial; Female; HIV; HIV Infections; Human immunodeficiency virus; Humans; Infections; Isoniazid; Laboratories; Male; Medical diagnosis; Medical screening; Medicine; Microbial Sensitivity Tests - methods; Microscopy; Multidrug resistant organisms; Mycobacterium tuberculosis - drug effects; Retrospective Studies; Rifampin; Sensitivity; Sputum; Studies; Surveillance; Tuberculosis; Tuberculosis, Multidrug-Resistant - diagnosis; Zimbabwe
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0055872

Limited data exist on use of the microscopic-observation drug-susceptibility (MODS) assay among persons suspected of MDR-TB living in high HIV-prevalence settings. We retrospectively reviewed available clinical and drug susceptibility data for drug-resistant TB suspects referred for culture and drug-susceptibility testing between April 1, 2011 and March 1, 2012. The diagnostic accuracy of MODS was estimated against a reference standard including Löwenstein-Jensen (LJ) media and manual liquid (BACTEC MGIT) culture. The accuracy of MODS drug-susceptibility testing (DST) was assessed against a reference standard absolute concentration method. One hundred thirty-eight sputum samples were collected from 99 drug-resistant TB suspects; in addition, six previously cultured MDR isolates were included for assessment of DST accuracy. Among persons with known HIV infection status, 39/59 (66%) were HIV-infected. Eighty-six percent of patients had a history of prior TB treatment, and 80% of individuals were on antituberculous treatment at the time of sample collection. M. tuberculosis was identified by reference standard culture among 34/98 (35%) MDR-TB suspects. Overall MODS sensitivity for M. tuberculosis detection was 85% (95% CI, 69-95%) and specificity was 93% (95% CI, 84-98%); diagnostic accuracy did not significantly differ by HIV infection status. Median time to positivity was significantly shorter for MODS (7 days; IQR 7-15 days) than MGIT (12 days; IQR 6-16 days) or LJ (28 days; IQR 21-35 days; p